update flutter version

Author: yulingtianxia

.github/workflows/dart.yml

@@ -18,10 +18,7 @@ jobs:
       - uses: subosito/flutter-action@v2
         with:
           # same with pubspec.yaml
-          flutter-version: "2.8.1"
-      - uses: maxim-lobanov/setup-xcode@v1
-        with:
-          xcode-version: latest-stable
+          flutter-version: "3.0.0"
       - run: flutter pub get
         working-directory: dart_native/example
       - run: flutter test --no-pub test/